A prior art breathing apparatus is described by J. L. Belcher in U.S. Pat. No. 1,901,219 which issued on Mar. 14, 1933. With the apparatus of Belcher a person is able to swim upon the surface of the water and descend to shallow depths while maintaining a cycle of unassisted respiration. The apparatus of Belcher consists of a float arranged to normally retain the open ends of an air intake tube and exhaled gases tube projecting above the surface of the water. The other end of the air intake tube is bifurcated with respective branches connecting into a pair of inlet ports provided in the sides of a breathing mask that covers the divers nose and mouth. Each inlet port is fitted with a one way flap-valve. The exhaled gases tube is connected to an exhaust port provided in the base of the mask and is fitted with a similar one-way flap-valve. The valve configuration and tubes of the apparatus of Belcher provide the wearer with a source of fresh air by the natural breathing process, while also prohibiting the rebreathing of exhaled gases.
One of the disadvantages of the apparatus of Belcher is that if the float supporting the air intake and exhaust tube is accidentally or deliberately pulled under the water surface, the entire apparatus will flood making it unusable until the water has been purged from the tubes. A further disadvantage is that the wearer's limit of descent is controlled by the overall length of the apparatus. Another disadvantage is the provision of the air intake tube, exhaust tube and non-return valves in connection with a breathing mask covering the wearer's nose and mouth. This prevents the person from wearing a conventional face mask. A still further disadvantage is the relative complexity of construction of the apparatus of Belcher, in particular the multiplicity of tubes, which makes the apparatus more expensive to make and clumsy to use.
The present invention was developed with a view to providing an improved snorkelling device for supplying air to a person by unassisted lung function to a depth of approximately one meter.